Receptor-interacting protein kinase 1 (RIPK1) regulates cell death and inflammation through kinase-dependent and -independent functions1,2,3,4,5,6,7. RIPK1 kinase activity induces caspase-8-dependent apoptosis and RIPK3 and mixed lineage kinase like (MLKL)-dependent necroptosis8,9,10,11,12,13. In addition, RIPK1 inhibits apoptosis and necroptosis through kinase-independent functions, which are important for late embryonic development and the prevention of inflammation in epithelial barriers14,15,16,17,18. The mechanism by which RIPK1 counteracts RIPK3–MLKL-mediated necroptosis has remained unknown. Here we show that RIPK1 prevents skin inflammation by inhibiting activation of RIPK3–MLKL-dependent necroptosis mediated by Z-DNA binding protein 1 (ZBP1, also known as DAI or DLM1). ZBP1 deficiency inhibited keratinocyte necroptosis and skin inflammation in mice with epidermis-specific RIPK1 knockout. Moreover, mutation of the conserved RIP homotypic interaction motif (RHIM) of endogenous mouse RIPK1 (RIPK1mRHIM) caused perinatal lethality that was prevented by RIPK3, MLKL or ZBP1 deficiency. Furthermore, mice expressing only RIPK1mRHIM in keratinocytes developed skin inflammation that was abrogated by MLKL or ZBP1 deficiency. Mechanistically, ZBP1 interacted strongly with phosphorylated RIPK3 in cells expressing RIPK1mRHIM, suggesting that the RIPK1 RHIM prevents ZBP1 from binding and activating RIPK3. Collectively, these results show that RIPK1 prevents perinatal death as well as skin inflammation in adult mice by inhibiting ZBP1-induced necroptosis. Furthermore, these findings identify ZBP1 as a critical mediator of inflammation beyond its previously known role in antiviral defence and suggest that ZBP1 might be implicated in the pathogenesis of necroptosis-associated inflammatory diseases.
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We thank Genentech and V. Dixit for Ripk3−/− mice, S. Akira for Zbp1−/− mice, and J. Han for lentiviral vectors. We thank B. Zevnik, P. Jankowski and S. Assenmacher at the CECAD Transgenic Core Facility for CRISPR/Cas9 mutagenesis in mouse zygotes and C. Uthoff-Hachenberg, J. Buchholz, E. Mahlberg and B. Kühnel for excellent technical assistance. Research reported in this publication was supported by funding from the ERC (grant agreement no. 323040) and the DFG (SFB829 and SFB670). J.L. was supported by a Humboldt research fellowship and C.K. was supported by a Humboldt research fellowship and an EMBO long-term fellowship.
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Bypassing drug resistance by triggering necroptosis: recent advances in mechanisms and its therapeutic exploitation in leukemia
Journal of Experimental & Clinical Cancer Research (2018)